Spatial-temporal potential exposure risk analytics and urban sustainability impacts related to COVID-19 mitigation: A perspective from car mobility behaviour

Coronavirus disease-2019 (COVID-19) poses a significant threat to the population and urban sustainability worldwide. The surge mitigation is complicated and associates many factors, including the pandemic status, policy, socioeconomics and resident behaviours. Modelling and analytics with spatial-temporal big urban data are required to assist...

Multimodal imaging combining time-domain near-infrared optical tomography and continuous-wave fluorescence molecular tomography

Fluorescence molecular tomography (FMT) emerges as a powerful non-invasive imaging tool with the ability to resolve fluorescence signals from sources located deep in living tissues. Yet, the accuracy of FMT reconstruction depends on the deviation of the assumed optical properties from the actual values. In this work, we improved the accuracy...

The Impact of Gate Recess on the H2 Detection Properties of Pt-AlGaN/GaN HEMT Sensors

The present work reports on the hydrogen gas detection properties of Pt-AlGaN/GaN high electron mobility transistor (HEMT) sensors with recessed gate structure. Devices with gate recess depths from 5 to 15 nm were fabricated using a precision cyclic etching method, examined with AFM, STEM and EDS, and tested towards H 2 response at high...

Random voids generation and effect of thermal shock load on mechanical reliability of light-emitting diode flip chip solder joints

To make the light-emitting diode (LED) more compact and effective, the flip chip solder joint is recommended in LED chip-scale packaging (CSP) with critical functions in mechanical support, heat dissipation, and electrical conductivity. However, the generation of voids always challenges the mechanical strength, thermal stability, and...

Discrete lattice fracture modelling of hydrated cement paste under uniaxial compression at micro-scale

A combination of laboratory experiments and numerical simulations at multiple length scales can provide in-depth understanding of fracture behaviour of hydrated cement paste (HCP). To that end, the current work presents a numerical study on compressive failure of hydrated cement paste (HCP) at the micro-scale. Virtual specimens consisting of...

The Impact of Gate Recess on the H₂ Detection Properties of Pt-AlGaN/GaN HEMT Sensors

The present work reports on the hydrogen gas detection properties of Pt-AlGaN/GaN high electron mobility transistor (HEMT) sensors with recessed gate structure. Devices with gate recess depths from 5 to 15 nm were fabricated using a precision cyclic etching method, examined with AFM, STEM and EDS, and tested towards H2 response at high...

High-resolution MEMS inertial sensor combining large-displacement buckling behaviour with integrated capacitive readout

Commercially available gravimeters and seismometers can be used for measuring Earth’s acceleration at resolution levels in the order of ng∕Hz (where g represents earth’s gravity) but they are typically high-cost and bulky. In this work the design of a bulk micromachined MEMS device exploiting non-linear buckling behaviour is described, aiming...

Impact of high temperature H₂ pre-treatment on Pt-AlGaN/GaN HEMT sensor for H₂S detection

In this paper, a method to extend the detection range of hydrogen sulfide (H₂S) gas sensor is demonstrated. The sensor is based on AlGaN/GaN high electron mobility transistors (HEMTs) with Pt gate. It is observed that the as-fabricated devices exhibited sensing signal saturation at 30 ppm H₂S exposure in dry air. A pre...

Design and characterization of zero magnetic field chambers for high efficiency neutron polarization transport

Several methods of polarized neutron scattering call for a zero magnetic field (ZF) region to reduce magnetic field integral aberrations while preserving the neutron polarization. Though the design for large angle neutron scattering has been presented in various places, the design characterization and tuning has not been discussed before. In...

Coupled hygro-mechanical finite element method on determination of the interlaminar shear modulus of glass fiber-reinforced polymer laminates in bridge decks under hygrothermal aging effects

To investigate the mechanical degradation of the shear properties of glass fiber-reinforced polymer (GFRP) laminates in bridge decks under hygrothermal aging effects, short-beam shear tests were performed following the ASTM test standard (ASTM D790-10A). Based on the coupled hygro-mechanical finite element (FE) analysis method, an inverse...

AlGaN/GaN HEMT micro-sensor technology for gas sensing applications

Wide bandgap gallium nitride material has highly favorable electronic properties for next generation power and high frequency electronic devices. A less widely studied application is highly miniaturized chemical and gas sensors capable of operating in harsh environment conditions. In this work we present our recent developments on design,...